Oxidation with terf-Butyl Hydroperoxide

Oxidation with tert-Butyl Hydroperoxide (TBHP) While catalytic amounts of CuCl resulted in poor yields of TMBQ with Oj as oxidant, the use of TBHP allowed for up to 80% yield with only 1.5wt% of CuCl and 2.8wt% of NH OH—HCl cocatalyst under ambient conditions [135]. The Ru-catalyzed oxidation of p-substituted phenols with TBHP gave corresponding (terf-butyldioxy) cyclohexadienones that can be converted to 2-substitutedp-BQ in the presence of a Lewis acid [136]. 

A similar increase in reactivities in the methyl-methylene-methine series is found in the free-radical oxidations of lower alkanes with oxygen in the presence of hydrogen bromide as an initiator of the reaction. Ethane gives a 64% yield of acetic acid at 220 °C, propane gives a 72% yield of acetone at 189 °C, and isobutane gives a 69.5% yield of terf-butyl hydroperoxide, a 10% yield of fm-butyl alcohol, and a 6% yield of di-rm-butyl peroxide at 163 °C [54],... 

In the field of asymmetric oxidation reactions the epoxidation of a,P-unsatu-rated carbonyl compounds was investigated. In the case of 1,4-naphthoquinone derivatives and terf-butyl hydroperoxide as reagents enantioselectivities up to 78% ee were observed with quininium and quinidinium salts as PT catalysts [40]. 

The first inverse of the ship-in-bottle synthesis, in which the zeolite cage is constructed around a porphyrin template, was reported by Li and Zhan. " The Fe(II) and Mn(II) derivatives of tetra(Af,A, Af-trimethylanilinium)porphyrin and H2(TMPyP) were used as cationic templates in zeolite hydrothermal synthesis. Attempts to incorporate an anionic porphyrin species, metallo-tetra(4-sulfunatophenyl)por-phyrin, were unsuccessful and trials with neutral TPP species resulted in trace encapsulation. High activity for the catalytic oxidation of cyclohexene by terf-butyl hydroperoxide was reported. 

The autoxidation of isobutane is now mainly carried out to obtain terf-butyl hydroperoxide [36]. Halogenated metalloporphyrin complexes are reported to be efficient catalysts for the aerobic oxidation of isobutane [18,37]. It was found that the oxidation of isobutane by air (lOatm) catalyzed by NHPI and Co(OAc)2 in benzoni-trile at 100 °C produced tert-butyl alcohol in high yield (81%) along with acetone (14%) (Eq. (6.3)) [38]. 2-Methylbutane was converted into the carbonacetic acid, rather than the alcohols, as prindpal products. These cleaved products seem to be formed via P-sdssion of an alkoxy radical derived from the decomposition of a hydroperoxide by Co ions. The extent of the P Scission is known to depend on the stability of the radicals released from the alkoxy radicals [39]. It is thought that the 3-scission of a terf-butoxy radical to acetone and a methyl radical occurs with more difficulty than that of a 2-methylbutoxy radical to acetone and an ethyl radical. As a result, isobutane produces terf-butyl alcohol as the principal product, while 2-methylbutane affords mainly acetone and acetic acid. 

Oxidation of thiophene or thiophene derivatives with various oxidants in the presence of dienophile iV-phenylmaleimide always leads to the Diels-Alder cycloaddition products. Typical oxidants H2O2/CF3CO2H [41], wt-CPBA [22, 42], m-CPBA/BF3 Et20 complex [13], and TPHP (terf-butyl hydroperoxide) [43] are shown in Schemes 27, 28, 29, and 30. The rhenium-catalyzed reactions are of... 

The oxidation of cyclohexene was carried out in a three neck flask imder an inert atmosphere. To a solution of cyclohexene (0.05 mol), terf-butyl hydroperoxide (0,14 mol) and 1,2,4-trichlorobenzene (0.05 mol) (used as internal standard) in chloroform (0.38 mol) 0,1 g of the catalyst was added. The reaction mixture was stirred at 50°C. All the samples were analyzed with a Trace GC Ultra (Fiimigan), fitted with an capillary column (10m, 0,1 mm, 0,4 pm) and an FID detector. Blanc reactions were performed without catalyst. 

Not only oxone bnt also other oxidants can be used in the preparation of hydroxy carbonyl derivatives. So, terf-butyl hydroperoxide has been used in the enantioselective oxidation of 2-alkoxycarbonyl indanone derivatives of type 33 catalyzed by cinchonine 35 to give the expected compound with moderated enantiomeric excess (50%). This chiral compound serves as the starting material for the synthesis of pyrazoline-type insecticide indoxacarb [102]. The use of chiral dihydroquinine (double bond hydrogenated compound 11) in combination with cumyl hydroperoxide at room temperature seems to be a more promising protocol, since the expected hydroxy carbonyl compounds could be obtained with excellent chemical yields and good enantiomeric excess [103]. 

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